This invention relates to gas turbine engines and particularly to the method of electron beam welding certain components to the split case construction.
The above cross-referenced patent application disclosed a method of fabricating a split case for a turbine type power plant. As noted therein the metal plate is rolled into a cylinder blank and butt welded, then grooved axially to accomodate a pair of mating flat plates that extend radially from the outer diameter, these plates are drilled to receive bolts and by turning the inner diameter of the cylinder to expose the inner edges of the flat plates the case becomes split and the flat plates serve as flanges to accommodate bolts that hold the two halves into place.
In certain engine models it is desirable to incorporate rails that extend radially and circumferentially around the outer diameter of the case. Additionally radial structural circumferential ribs are formed on the outer diameter of the case. Inasmuch as it is necessary to weld the flanges into place and because of the material selected, say titanium or an alloy thereof, electron beam welding has become essential to the construction thereof. The flanges and rails however present welding problems that are solved by the present invention.
According to this invention we have constructed a split case by electron beam welding the mating flanges to the case and each half of the flange is constructed with a base, extending rib and rail that allow for constant metal exposure to the electron beam as it travels along the welding surfaces. The "L" shaped rails adjacent the flange are cut away to allow exposure to the welding surface and to avoid having the electron beam penetrating the vertical leg of the "L". The slot or groove is undercut so that the flanges extending into the groove sets below the cutting surface. In this manner the inner diameter and the inner edge of the flange are turned concomitantly to assure an integral and uniform internal surface of the cylinder.